To "cause trouble" is to do something that makes problems for other people.

"Trouble" can include things like arguments and disagreements. But people also say that you're "causing trouble" if you make requests or suggestions that cause people to have to work a lot harder. For example, if there's someone at work who points out extra work that needs to be done, you can ask a coworker:

Why is he always causing trouble?

"Cause trouble" is used in some set phrases like "I hate to...". Another phrase that you can use with "cause trouble" is "I didn't mean to...":

I didn't mean to cause any trouble.

You use this when you did something that made problems for people, but you don't want people to think you did it on purpose.